The present invention relates to an eyeglass-frame, and more particularly relates to an improved construction of bows for an metallic eyeglass-frame.
An eyeglass-frame in general includes a pair of rims each holding a lense, a bridge for connecting the rims, a pair of decorations or lugs projecting sideway from the associated rims, a pair of cringles or pads attached to the facing edges of the rims below the bridge, and a pair of bows or sides extending rearwards from the associated decorations.
Among these parts, the bows are most important elements in the construction and function of the eyeglass-frame. The bows are required to stably and constantly hold the eyeglasses on the face of a wearer so that the beam axes of the lenses should be kept at correct positions relative to the eyes of the wearer. It is also required for the bows to hold the eyeglasses without imposing any discomfort on the wearer and without causing any fatigue of the wearer even after long use of the eyeglasses.
Conventionally, metallic materials such as copper alloys, stainless steel and nickel have been used for eyeglass-frames. These metallic materials, however, have an inherent nature to develope so-called plastic deformation when an external force above a certain level is applied to them, in particular when such large force is applied repeatedly. As a consequence, when the bows are excessively pulled sideways during use of the eyeglasses, such plastic deformation tends to be developed on the bows and prevents correct holding of the eyeglasses on the face of the wearer. In other words, the initially set positioning of the beam axis of the lenses relative to the wearer's eyes is seriously disturbed and the eyeglasses no longer rest stably on the face of the wearer. Depending on the mode of the plastic deformation, the bows may impose increased contact pressure on the surface of the wearer, thereby causing increased discomfort on the wearer. In addition, change in temperature of the environment greatly influences the mode of fitting of the bows to the face of the wearer in particular in facial sections such as the temples and ear lobes of the wearer.